A key may be used in cryptography to determine the functional output of a cryptographic process or cipher. Without a key, the process may produce useless results. With respect to encryption, a key facilitates the particular transformation of plaintext into ciphertext, or vice versa during decryption. A key may also be used in a variety of cryptographic processes, such as digital signature schemes and message authentication codes.
A personal identification number (PIN) is typically a numeric password shared between a user and a system for authenticating the user to the system. Once the user is authenticated, the system may securely communicate with another system by using a key. Typically, the user provides a non-confidential user identifier and a confidential PIN to gain access to the system. The user may be granted access to the system when the PIN entered matches a corresponding number stored in the system.